Measuring devices and sensors are known which are arranged on a connector, adapter, or spacer between individual sections of a line. The line guides a fluid—in particular, an isotonic saline solution or other crystalloid infusion solutions or blood—the property of which—in particular, pressure—is to be recorded. In such measuring devices, there is often the risk of coagulation (or so-called blood clotting) or hemolysis—in particular, as a result of edges, undercuts, or fluidically unfavorable transitions. The connecting elements or connectors also increase the risk of leakages—in particular, on interfaces between a connector and an extra-corporeal hose kit or in the measuring system—and must be additionally checked. In particular, the problem is known from practice that leakages can occur, e.g., on Luer connections. Especially in the case of extra-corporeal circulation, there is then the risk that air can potentially be sucked into a discharge line, in which there can be a low pressure, and mixed with the fluid/blood. From a feed line in which there can be an overpressure, there is the potential for fluid/blood to be squeezed out of the line. In this case, the sterility of the overall device can no longer be ensured. In addition, the connector or adapter must be mounted on the line, and a seal, bonded joint, or other interface, which is as sterile as possible or which can be sterilized, must be able to be ensured.
As an alternative to such measuring devices or sensors coupled or integrated in the line, a measurement—in particular, a pressure measurement—can also be effected outside the line. The corresponding sensor can then directly record a pressure, e.g., by means of a water column. However, a so-called priming operation is required for this type of pressure measurement, in order to be able to start the pressure measurement. With priming, the hose system is filled with a crystalloid solution, such as isotonic saline solution (NaCl), after which the hose system is vented. There is a risk that the venting of the line/hose system will be carried out incorrectly. During the measurement, there is a risk that fluid/blood penetrating the crystalloid solution in a line leading to a measuring sensor might impair or interrupt the measuring process, which can be life threatening.
Also disadvantageous in this type of pressure measurement are measuring errors, which are caused by gas inclusions in the water column. Also, in most cases, the pressure measurement itself can be performed only with a delay, since a pressure wave must first be transferred through the water. Therefore, such a direct pressure measurement makes it difficult, for example, to synchronize a pump with the arterial pressure curve of the patient.
The German patent application (Offenlegungsschrift) DE 10 2005 063 410 A1 describes a blood vessel catheter in which a blood pressure sensor is arranged on a housing which is coupled to a catheter tube.
The German patent application (Offenlegungsschrift) DE 10 2007 038 402 A1 describes a device for recording a pressure in which a sensor element is embedded in the wall structure of a line separate from a medium guided along the line.
The European patent specification EP 0 328 558 B1 describes an elastic hose on whose internal surface a coating is applied in which a pressure signal can be measured when the hose is deformed.